Two-system dynamic earphone



Nov. 24, 1964 R. GRIKE 3,158,697

TWO-SYSTEM DYNAMIC EARPHONE Filed April 4, 1962 INVENTOR:

Rudolf GRIKE BY v Wfl g' b AGENT United States Patent O Pce 3,ltl,697 TWG-SYSTEM DYNAMlC EARPHONE Rudolf Griire, Vienna, Austria, assigner to Akustische u. Kino-Gerte Geseiischaft mhd-I., Vienna, Austria Filed Apr. e, i962, Ser. No. 185,157 Claims priority, application Austria, Apr. 28, 1961, At 3,350/61 d Claims. (Qi. 179mm@ The advances made in electro-acoustics have led to increasing requirements regarding the quality of the reproduction of sound by electro-acoustic transducers.

These requirements have been met in one-channel systems by the development of special loudspeakers, particularly of highand low-tone loudspeakers so that systems of high quality, which fulfil virtually all requirements, can be installed with a corresponding expenditure. The expenditure is even higher when a stereophonic reproduction of sound events is desired. For this reason, many music lovers listen to stereophonic recordings with earphones.

Only high--grade earphones being suitable for this purpose, the still widely used electro-magnetic earphone systems have been superseded by dynamic systems, which have a more uniform frequency response and a large frequency range. It has now been found that even these transducers do not always meet all higher requirements and a further improvement thereof is desirable. Difliculties arise particularly when the earphone does not tightly contact the ear.

The invention relates to an improvement in dynamic earphones and resides in that the earphone incorporates two actuating systems which are concentric relative to each other and of which suitably the inner one serves for a preferential reproduction of the high tones while the outer system serves for a preferential reproduction of the low tones, the diaphragm of the low-tone system preferably extending into the recessed earpiece.

rl`he advantage afforded by the invention resides in that each system can be optimally designed for the frequency range associated with it to achieve a substantial increase of the overall frequency range transmitted by the earphone. The application of the dynamic system minimizes the non-linear distortions.

Whereas it is already known in the design of loudspeakers to provide concentric arrangements of high-tone and low-tone systems, a similar proposal for earphones has not yet been disclosed in spite of the highly advanced state of the art. It was apparently believed that the space available was not sutiicient to accommodate two systems, one of which may even have a relatively large diaphragm, or it was beiieved that the use of two systems in the earpiece of an earphone would not result in an advantage.

Whereas the low-tone diaphragm of the earphone may have a soft mounting, the high-tone diaphragm may have a hard mounting and may be adjoined on the rear by an air chamber of small depth. This enables a strong reproduction of the basses in conjunction with a full reproduction of the high frequencies even when the earphone is only loosely applied to the ear.

Thorough investigations and measurements have shown that the increase in quality is considerable, even when the earphone does not tightly contact the ear.

An illustrative embodiment of the invention is shown in FIG. l of the accompanying drawing, FIG. 2 being an explanatory diagram.

A housing 1 having an inclined dange 1a contains in the axis of the earphone the magnetic boss 3 for the hightone system including the inner diaphragm 4- and the moving coil da. This system may be surrounded by a pot-shaped part 5 of soft iron. This part of soft iron not only forms the yoke for completing the magnetic cir- 3,158,697 Patented Nov. 24, .1964

cuit of the internal high-tone system but at its outside defines a portion of the outer annular gap 14 for the lowtone system, for which an annular permanent magnet 6 is provided. The yoke member 5 has a peripheral an- 5y nular rib 10 which supports the rim of the diaphragm 4 to establish a relatively stiff or hard mounting for this diaphragm for the reasons previously explained. A shallow air space between diaphragm 4 and the front face of member 5 communicates through the inner annular air gap 11, receiving the voice coil 4a, with an air chamber 12 surrounding the magnetic boss 3. The low-tone outer diaphragm 7, provided with a moving coil 7a in gap 14, has a rim engaging a circular step 1b ofthe housing flange 1a and is secured to this flange, eg., by an adhesive connection. This iange 1a supports the rim of the diaphragm 7 through the intermediary of a corrugated suspension 13 establishing a relatively flexible or soft mounting for this diaphragm 7, .again for the reasons noted above. The housing flange 1a carries at its outer rim a screw thread onto which is screwed an earpiece 8 which covers and protects .at the same time the diaphragm 7 of the low-tone system without impeding the movements of said diaphragm. Earpiece 8 is formed with a central aperture 15 facing the magnetic structure 3, 5. Openings 9 leading to the atmosphere are filled in known manner by a frictional acoustic resistance material to ensure a strong reproduction of the basses even when the earphone does not tightly contact the ear. An earphone provided with tWo earpieces according to the invention is particularly suitable for a reproduction of stereophonic recordings with perfect fidelity.

FIG. 2 shows the frequency curve of an earphone having only one diaphragm, measured on a coupler of 2 cubic centimeters. The hatched yarea is that range which is improved by the earphone according to the invention having two diaphragms. In this graph the pressure response of the earphone, in microbars per volt, is plotted against frequency given in cycles per second.

Instead of magnetic systems having two concentric air gaps, both moving coils may be disposed in a single annular air gap, as is known in loudspeakers. The design of the magnetic system and the arrangement of the diaphragms may be similar to those adopted in loudspeakers. The necessary reduction in the size of the elements of construction is facilitated by the progress in magnetic engineering. The tuning of the diaphragms and the adjustment of the efficiency `of the individual transducers may be elfected with known electrical, mechanical or magnetic means.

What is claimed is:

l. A dynamic earphone which comprises at least one earpiece having a portion adapted to contact a human ear, said portion defining an annular cavity, said earpiece incorporting inner and outer actuating systems which are concentrically arranged relative to each other and comprise each a diaphragm and a movable coil energizable to actu-ate said diaphragm, said inner system being designed for a preferential reproduction of relatively high tones and said outer system being designed for a preferential reproduction of relatively low tones, said diaphragm of said outer system extending into said cavity.

2. A dynamic earphone as defined in claim l wherein said diaphragm of said outer system is peripherally provided with suspension means securing it to said portion Within said cavity and forming a relatively soft mounting for the last-mentioned diaphragm, said inner actuating system being provided with support means peripherally engaging the diaphragm of said inner system and forming a relatively hard mounting therefor.

3. A dynamic earphone comprising at least one earpiece having a front surface shaped to contact a human ear, a housing rigid with said earpiece on the rear side amasar n thereof, a magnetic structure in said housing forming an inner and an outer annular air gap concentrically disposed therein, an inner diaphragm spanning the central part of said structure land extending across said inner air gap, relatively stil mounting means peripherally supporting said inner diaphragm on said structure externally of said inner air gap and with slight spacing from the front of said structure whereby a shallow air space is formed rearwardly of said inner diaphragm, an outer diaphragm `overlying said inner diaphragm and extending radially therebeyond across said outer air gap, relatively llexible mounting means peripherally supporting said outer diaphragm on said housingsaid structure forming within said housing an air chamber communicating through said inner air gap with said shallow air space, a first movable voice coil on said inner diaphragm in said inner air gap, and a second movable voice coil on said outer diaphragm in said outer air gap.

4. A dynamic earphone as defined in claim 3 wherein said earpiece partly overlies said outer diaphragm and is provided with a central aperture exposing a portion of said outer diaphragm registering with said inner diaphragm, said housing being provided with passages leading to the atmosphere at locations behind said outer diaphragm toverlain by said earpiece, said passages containing frictional acoustic resistance material.

References Cited in the tile of this patent UNITED STATES PATENTS 1,951,692 Evens Mar. 20, 1934 2,122,587 Ringel July 5, 1938 FOREIGN PATENTS 1,001,734 France Feb. 27, 1952 

1. A DYNAMIC EARPHONE WHICH COMPRISES AT LEAST ONE EARPIECE HAVING A PORTION ADAPTED TO CONTACT A HUMAN EAR, SAID PORTION DEFINING AN ANNULAR CAVITY, SAID EARPIECE INCORPORATION INNER AND OUTER ACTUATING SYSTEMS WHICH ARE CONCENTRICALLY ARRANGED RELATIVE TO EACH OTHER AND COMPRISE EACH A DIAPHRAGM AND A MOVABLE COIL ENERGIZABLE TO ACTUATE SAID DIAPHRAGM, SAID INNER SYSTEM BEING DESIGNED FOR A PREFERENTIAL REPRODUCTION OF RELATIVELY HIGH TONES AND SAID OUTER SYSTEM BEING DESIGNED FOR A PREFERENTIAL REPRODUCTION OF RELATIVELY LOW TONES, SAID DIAPHRAGM OF SAID OUTER SYSTEM EXTENDING INTO SAID CAVITY. 